A small group of FBI agents huddled outside a Home Depot in Atlanta in January 2006, watching a young man suspected of being linked to terrorists as he walked out the door with materials that could be used to make a bomb.
They knew Syed Haris Ahmed had researched bomb-making techniques online and shaved his head, as some jihadis have done before an attack. However, they had to make a quick decision faced by other terror investigators across the country: They could swoop in and keep him from potentially building a bomb, which could leave them with a case too weak to win a conviction. Or they could keep building a stronger case _ and risk a potential terror attack.
"If we have a terrorist event, we could solve what happened. But that means we've lost," said Rick Maxwell, an assistant special agent in charge in Atlanta. "What we want to do is prevent them. It's much more difficult, but that's our goal."
In the end they held off, relying on federal explosive experts who told them the PVC pipe was not enough to create a dangerous explosive. They also sent local police pretending to be on a routine call to question Ahmed about the piping, which they determined was being used for a school project.
Ahmed and co-defendant Ehsanul Islam Sadequee were ultimately convicted of terror-related charges earlier this year, and federal prosecutors said the case exemplified their strategy of snuffing out potential plots in their earliest stages. Sadequee faces up to 60 years in prison, and Ahmed faces 15 years behind bars when the pair is sentenced Monday.
However, federal investigators have a mixed record when other terrorist plots are broken up early. Five Muslim immigrants were convicted last year of conspiring to kill U.S. soldiers at Fort Dix in New Jersey, but they were acquitted of attempted murder after prosecutors acknowledged they were likely months away from acting.
Meanwhile, the FBI has recently been criticized for not launching a deeper investigation into Maj. Nidal Hasan, who is accused of shooting and killing 13 people Nov. 5 at Fort Hood, Texas _ even though agents had intercepted at least 18 e-mails between him and a radical Muslim cleric.
The way the bureau handled information about Hasan before the rampage is currently being reviewed.
Pursuing charges before all the evidence is in hand can backfire _ suspects have sued authorities before, claiming they were falsely imprisoned victims of witch hunts, said Jeffrey Addicott, director of the Center for Terrorism Law at St. Mary's University in San Antonio.
It can also confine prosecutors, who may only have enough evidence to charge suspects with lesser crimes like identity theft and lying to federal investigators rather than conspiracy to commit murder or providing material support to a terrorist group.
Addicott, though, said he's noticed investigators have been more cautious in the past few years.
"I think the reason we were a bit trigger-happy was Sept. 11, but we're starting to get more patient," he said.
The Atlanta terror investigation started as many do: with a tip about Sadequee.
Investigators found a string of anti-American rhetoric, possible links to suspected terrorists in foreign countries and an e-mail sent by Sadequee in 2001 in which he said he wanted to join the Taliban in Afghanistan.
It was enough to delve deeper in the case. Eventually, the FBI dispatched four surveillance teams to track Ahmed, Sadequee and others believed to be involved. The lead investigators were working weekends, holidays and could hardly sleep through the night without getting an update. Greg Jones, the FBI's agent in charge in Atlanta, was getting daily briefings on the case.
As many as 150 people worked to slowly gather evidence that Sadequee met other extremists as he delved deeper into online forums devoted to violent jihad, Jones said.
One was Ahmed, a former Georgia Tech student. Authorities said the two took a bus to Toronto in March 2005 and met with at least three other subjects of a federal investigation to discuss possible attack sites. A month later, the pair drove Ahmed's pickup truck to Washington, D.C., to videotape 62 choppy clips of U.S. landmarks.
One of the videos, which was eventually played for jurors, showed the two driving as Sadequee said: "This is where our brothers attacked the Pentagon."
Authorities made their move in early 2006, arresting Ahmed in March and Sadequee a month later in Bangladesh. In separate trials, both sought to portray their online discussions about jihad as empty talk. Sadequee, who like Ahmed represented himself at trial, said he never considered following through on the boastful chatter.
"We were immature young guys who had imaginations running wild," Sadequee told jurors in his closing arguments in August. "But I was not then, and am not now, a terrorist."
When the two were convicted over the summer, a wave of relief washed over the investigators. But Jones said they wouldn't have waited if they knew something was going to happen.
"Public safety wins out every time," Jones said. "The slightest hint that an individual possesses something that can harm or kill, you let the case go to hell."